There has been a great deal of demand for a linear or rotary position sensing apparatus that determines nonintrusively the position of a mechanical target member such as a float floating on the free surface of a liquid medium, a drag body suspended in the stream of a fluid medium, a pointer marking a scale in a dial or bar gauge, a position of a linear or rotary actuator, a nonrotating propeller or turbine experiencing a fluid dynamic torque, etc., which apparatus provides an inexpensive means for automatically or remotely measuring or monitoring the position of the mechanical target with a high degree of resolution and a great deal of accuracy. Unfortunately, such a position sensing apparatus of high performance and low cost is not available at the present time.